Sansha Electric Manufacturing Company, Limited

Hiroki Morimoto

Kenzo Danjo

Tatsuya Kawabata

Tetsuro Ikeda

Takashi Tsujii

A power supply circuit () is responsive to an activating signal by supplying a discharge lamp () with an operating voltage on which a high voltage is temporality superposed. An insufficient current detecting circuit () detects abnormality of an output current supplied to the discharge lamp () from the power supply circuit (). A CPU () stops the operation of the power supply circuit () in response to detection of abnormality by the insufficient current detecting circuit (). An output nullification time period timer () nullifies the output of the insufficient current detecting circuit () for a predetermined time period measured from the supplying of the activating signal.

Discharge lamp igniting apparatus

Each of master and slave switching power supply apparatuses () has an IGBT (or) switching-controlled by a PWM pulse signal produced, based on a clock signal, by a switching device driving PWM pulse output section (or), to thereby provide DC power in parallel to a load (). The clock signal produced in the master switching power supply apparatus () is coupled to the slave switching power supply apparatus () through a photocoupler () in the master switching power supply apparatus () and a photocoupler () of the slave switching power supply apparatus (). Also, the clock signal developed at the output of the photocoupler () is coupled through a photocoupler () to the master switching power supply apparatus (). The photocouplers () have the same delay characteristic.

Parallel-operating power supply system

An output of a rectifying circuit (), which rectifies commercial AC power, is supplied to an inverter () through a power factor correction circuit (). The output of the inverter () is voltage-transformed in a transformer (), rectified in a rectifying circuit () and is applied to a xenon lamp (). A secondary winding () of a transformer () of an igniter () is connected between the rectifying circuit () and the xenon lamp () in order to generate an arc in the xenon lamp (). A pulse generator provides a pulse for a short time period to a primary winding () of the transformer (). An auxiliary power supply () supplies arc-sustaining current prepared based on the commercial AC power to the junction of the rectifying circuit () and the secondary winding () of the transformer ().

Power supply apparatus for arc-generating load

Lighting of a discharge lamp is controlled in a manner to reduce deterioration of the discharge lamp subjected to high temperature and extend the lifetime of the discharge lamp. A method for controlling lighting of the discharge lamp includes a first constant current control process (period T, which corresponds to steps Sand S) in which constant current control is executed by supplying a first current to the discharge lamp, a second constant current control process (period T, which corresponds to steps Sand S) in which constant current control is executed by supplying a second current greater than the first current to the discharge lamp after the first constant current control process, and a constant power control process (period T) in which constant power control is executed after the second constant current control process.

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Osaka, Japan

Hiroki Morimoto